20 15 Audi A4L exhaust fault light goes off, indicating insufficient air flow.

The fault light caused by the fault of the air flowmeter is on. The air flow meter is installed between the air cleaner housing and the air inlet hose. The air flow meter checks the air intake of the engine, converts the air intake information into an electrical signal, and transmits it to the electronic control unit ECU for calculating the appropriate fuel injection quantity. If the air filter element is seriously polluted or infiltrated, polluted particles or liquid may enter the air flowmeter, resulting in the wrong measured air quality value, which will lead to problems such as insufficient air intake and insufficient power, because the calculated fuel injection quantity is incorrect.